Optoelectronic device

ABSTRACT

An optoelectronic device, including: a support; at least one first electrically-conductive layer covering the support; display pixel circuits including first and second opposite surfaces bonded to the first electrically-conductive layer, each display pixel circuit including an electronic circuit including the first surface and a third surface opposite to the first surface, the first surface being bonded to the first electrically-conductive layer, and at least one optoelectronic circuit bonded to the third surface and including at least one light-emitting diode, at least one of the electrodes of the light-emitting diode being connected to the electronic circuit by the third surface; at least one second electrically-conductive layer covering the display pixel circuits and electrically coupled to the electronic circuits of the display pixel circuits on the side of the second surface.

This Application is a national stage filing under 35 U.S.C. § 371 ofInternational Patent Application Serial No. PCT/FR2018/051849, filedJul. 19, 2018, which claims priority to French patent applicationFR17/56984, filed Jul. 21, 2017, the contents of these applications areincorporated herein by reference in their entirety.

BACKGROUND

The present disclosure concerns an optoelectronic device, particularly adisplay screen or an image projection device, comprising light-emittingdiodes, called LEDs hereafter, based on semiconductor materials, andtheir manufacturing methods.

DISCUSSION OF THE RELATED ART

A pixel of an image corresponds to the unit element of the imagedisplayed by the optoelectronic device. When the optoelectronic deviceis a color image display screen, it generally comprises, for the displayof each pixel of the image, at least three components, also calleddisplay sub-pixels, which each emit a light radiation substantially in asingle color (for example, red, green, and blue). The superposition ofthe radiations emitted by the three display sub-pixels provides theobserver with the colored sensation corresponding to the pixel of thedisplayed image. In this case, the assembly formed by the three displaysub-pixels used to display a pixel of an image is called display pixelof the optoelectronic device.

Each display sub-pixel may comprise a light source, particularly alight-emitting diode, for example, made up of semiconductor materials. Aknown method of manufacturing an optoelectronic device, particularly adisplay screen or an image projection device, comprising light-emittingdiodes, called “pick and place” method, comprises manufacturing thelight-emitting diodes in the form of separate components and placingeach light-emitting diode at a desired position on a support which maycomprise conductive tracks for the electric connection of thelight-emitting diodes.

A disadvantage of such a method is that it generally requires accuratelyplacing the light-emitting diodes on the support. This requiresimplementing alignment methods which are all the more complex as thedimensions of the light-emitting diodes are decreased.

Another disadvantage of such a method is that an increase in theresolution of the optoelectronic device results in an increase in thenumber of transfers of light-emitting diodes onto the support and thusin an increase in the duration of the optoelectronic devicemanufacturing, which may be incompatible with a manufacturing at anindustrial scale.

To form a large LED display made up of assembled unit LED components,the LEDs should be assembled with control circuits which control anumber of LEDs. The different units are coupled together by wires. Suchan assembly decreases the quantity of data that can be transmitted andit is difficult to display a video stream.

For micrometer-range LED displays, called μLEDs hereafter, for theformats of TV, tablet, smart phone type which are being developed byseveral manufacturers, an active array is necessary to display a videostream with a high resolution. Currently, active arrays for displays areformed in thin film transistors, or TFTs. TFTs use deposits of amorphoussilicon or polysilicon on large glass surface areas and require usingcomplex microelectronics methods on large surface areas.

The use of so-called smart pixels integrating control electronics withthe LEDs or μLEDs may enable to form TFT-free active arrays. Such activearrays may be formed on very large surface areas since they are based onthe electronics embarked under the pixel. On the other hand, suchelectronics would benefit from the performance of the silicon-basedtechnology. Large outdoor or indoor screens integrating this technologymay be controlled by active matrix, thereby increasing their brightnessand, further, may display larger data streams.

Another advantage of the approach is the forming of large screens with avery large number of pixels. No constraint is imposed by predefined TFTactive matrices or by electronics to be assembled.

SUMMARY

Thus, an object of an embodiment is to at least partly overcome thedisadvantages of the previously-described optoelectronic devicescomprising light-emitting diodes.

Another object of an embodiment is to decrease the number of transfersof components onto the support of the optoelectronic device during themanufacturing of the optoelectronic device.

Another object of an embodiment is to decrease accuracy constraints onplacing of components on the support of the optoelectronic device.

Another object of an embodiment is for optoelectronic devices to becapable of being manufactured at an industrial scale and at a low cost.

Another object is for the optoelectronic device to comprise an activearray.

Another object is for the optoelectronic device to enable to display avideo stream.

Thus, an embodiment provides an optoelectronic device comprising:

a support;

at least one first electrically-conductive layer covering the support;

display pixel circuits comprising first and second opposite surfaces,bonded to the first electrically-conductive layer, each display pixelcircuit comprising an electronic circuit comprising the first surfaceand a third surface opposite to the first surface, the first surfacebeing bonded to the first electrically-conductive layer, and at leastone optoelectronic circuit bonded to the third surface and comprising atleast one light-emitting diode, at least one of the electrodes of thelight-emitting diode being connected to the electronic circuit by thethird surface;

at least one second electrically-conductive layer covering the displaypixel circuits and electrically coupled to the electronic circuits ofthe display pixel circuits on the side of the second surface.

According to an embodiment, the device further comprises anelectrically-insulating layer covering the first electrically-conductivelayer between the display pixel circuits.

According to an embodiment, the electrically-insulating layer covers thelateral sides of the display pixel circuits.

According to an embodiment, each display pixel circuit further comprisesan electrically-insulating portion covering the electronic circuit andthe optoelectronic circuit and at least one electrically-conductiveelement crossing the electrically-insulating portion and electricallycoupled to the second electrically-conductive layer and to theoptoelectronic circuit or to the electronic circuit.

According to an embodiment, for each display pixel circuit, theoptoelectronic circuit comprises a through connection electricallyinsulated from the rest of the optoelectronic circuit and electricallycoupled to the electronic circuit and to the conductive element.

According to an embodiment, the device comprises at least two firstseparate electrically-conductive layers and covering the support,assemblies of said display pixel circuits bonded to each firstelectrically-conductive layer, and at least two secondelectrically-conductive layers, each covering one of the assemblies ofsaid display pixel circuits and each being electrically coupled to theelectronic circuits of one of the assemblies of said display pixelcircuits.

According to an embodiment, the device comprises a unit for supplying,between the first electrically-conductive layer and the secondelectrically-conductive layer, a voltage modulated by control signals,the electronic circuit of each display pixel circuit being capable ofdemodulating said voltage to extract the control signals.

According to an embodiment, each electronic circuit comprises a memoryhaving an identifier stored therein, the identifiers stored in theelectronic circuits being different, and each electronic circuitcomprises circuits capable of extracting from the modulated voltageinformation representative of one of the identifiers.

According to an embodiment, the device comprises at least one waveguide,possibly integrated to the second electrically-conductive layer, coupledto the optoelectronic circuits of the display pixel circuits and capableof guiding an electromagnetic radiation.

According to an embodiment, the device further comprising a source ofsaid electromagnetic radiation coupled with the waveguide and, for eachdisplay pixel circuit, the optoelectronic circuit comprises a sensor ofsaid electromagnetic radiation capable of supplying a measurement signalto the electronic circuit.

According to an embodiment, the source is capable of modulating theelectromagnetic radiation with control signals and, for each displaypixel circuit, the electronic circuit is capable of demodulating themeasurement signal to extract the control signals.

According to an embodiment, the device comprises at least twowaveguides, possibly integrated to the second electrically-conductivelayer coupled to the optoelectronic circuits of different assemblies ofsaid display pixel circuits.

According to an embodiment, the device further comprises means ofoptical coupling between the waveguide and at least some of the displaypixel circuits.

An embodiment provides a method of manufacturing an optoelectronicdevice, comprising the steps of:

a) manufacturing display pixel circuits comprising first and secondopposite surfaces and each comprising an electronic circuit comprisingthe first surface and a third surface opposite to the first surface, andat least one optoelectronic circuit bonded to the third surface andcomprising at least one light-emitting diode, at least one of theelectrodes of the light-emitting diode being connected to the electroniccircuit by the third surface;

b) manufacturing a support covered with at least one firstelectrically-conductive layer;

c) bonding the first surface of the electronic circuit of each displaypixel circuit to the first electrically-conductive layer;

d) forming at least one second electrically-conductive layer coveringthe display pixel circuits and electrically coupled to theoptoelectronic circuits of the display pixel circuits on the side of thesecond surface.

According to an embodiment, the method comprises, between steps c) andd), the step of forming an electrically insulating layer covering thefirst electrically-conductive layer between the display pixel circuits.

According to an embodiment, step a) comprises forming, for each displaypixel circuit, an electrically-insulating portion covering theelectronic circuit and the optoelectronic circuit and at least oneelectrically-conductive element crossing the electrically-insulatingportion and electrically coupled to the second electrically-conductivelayer and to the optoelectronic circuit or to the electronic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will be discussed indetail in the following non-limiting description of specific embodimentsin connection with the accompanying drawings, in which:

FIGS. 1 and 2 respectively are a lateral cross-section view and a topview, partial and simplified, of an embodiment of an optoelectronicdevice;

FIG. 3 is an equivalent electric diagram of a display pixel of theoptoelectronic device shown in FIGS. 1 and 2 ;

FIGS. 4A and 4B are partial simplified lateral cross section views ofother embodiments of an optoelectronic device;

FIG. 5 is an equivalent electric diagram of a display pixel of theoptoelectronic device shown in FIG. 4B;

FIG. 6 is a partial simplified top view of the optoelectronic deviceshown in FIGS. 1 and 2 illustrating an advantage of the optoelectronicdevice manufacturing method;

FIG. 7 is a diagram illustrating the control of the optoelectronicdevice shown in FIG. 1 or 4 ;

FIGS. 8A and 8B are partial simplified top views of other embodiments ofan optoelectronic device;

FIG. 9 is a partial simplified lateral cross-section view of anotherembodiment of an optoelectronic device;

FIGS. 10 to 12 are partial simplified top views of other embodiments ofoptoelectronic devices;

FIGS. 13 and 14 are timing diagrams respectively of the potentialsapplied to the conductive strips coupled to a display pixel to becontrolled and of the voltage seen between the power supply terminals ofthe display pixel to be controlled;

FIG. 15 shows an equivalent electric diagram of an embodiment of adisplay pixel;

FIG. 16 shows an equivalent electric diagram of a portion of the displaypixel of FIG. 15 ;

FIG. 17 shows a timing diagram of signals during the operation of thedisplay pixel of FIG. 15 ;

FIGS. 18 to 21 show equivalent electric diagrams of portions of thedisplay pixel of FIG. 15 ;

FIG. 22 shows a timing diagram of signals during the operation of thedisplay pixel having a control unit in accordance with the embodimentshown in FIG. 18 ;

FIG. 23 shows an equivalent electric diagram of another embodiment of adisplay pixel;

FIGS. 24 and 25 show equivalent electric diagrams of portions of thedisplay pixel of FIG. 23 ;

FIG. 26 shows a timing diagram of signals during the operation of thedisplay pixel of FIG. 23 ;

FIGS. 27A to 27I are partial simplified lateral cross section views ofstructures obtained at successive steps of another embodiment of amethod of manufacturing the optoelectronic device shown in FIGS. 1 and 2; and

FIGS. 28A to 28D are partial simplified lateral cross section views ofthe structures obtained at successive steps of another embodiment of amethod of manufacturing the optoelectronic device shown in FIG. 4B.

DETAILED DESCRIPTION

For clarity, the same elements have been designated with the samereference numerals in the various drawings and, further, as usual in therepresentation of electronic circuits, the various drawings are not toscale. Further, only those elements which are useful to theunderstanding of the present disclosure have been shown and will bedescribed. In particular, the structure of a light-emitting diode iswell known by those skilled in the art and has not been described indetail.

In the following description, when reference is made to terms qualifyingthe relative position, such as term “top”, “below” “upper”, or “lower”,etc., reference is made to the orientation of the drawings or to anoptoelectronic device in a normal position of use. Unless otherwisespecified, terms “about”, “approximately”, and “in the order of” mean towithin 10%, preferably to within 5%. Further, the “active area” of alight emitting diode designates the region of the light-emitting diodefrom which most of the electromagnetic radiation provided by thelight-emitting diode is emitted. Further, a signal which alternatesbetween a first constant state, for example, a low state, noted “0”, anda second constant state, for example, a high state, noted “1”, is called“binary signal”. The high and low states of different binary signals ofa same electronic circuit may be different. In particular, the binarysignals may correspond to voltages or to currents which may not beperfectly constant in the high or low state.

FIGS. 1 and 2 show an embodiment of an optoelectronic device 10, forexample, corresponding to a display screen or to an image projectiondevice, comprising display pixels, two display pixels being shown inFIG. 1 and three display pixels being shown in FIG. 2 . FIG. 1 is across-section view of FIG. 2 along line II-II and FIG. 2 is across-section view of FIG. 1 along line I-I.

Device 10 comprises, from bottom to top in FIG. 1 :

a support 12, comprising opposite lower and upper surfaces 14, 16,preferably parallel;

a first electrode layer 18 comprising an electrically conductive layer18 covering upper surface 16;

display pixels Pix, also called display pixel circuit hereafter, restingon electrode layer 18 and in contact with electrode layer 18, andcomprising a lower surface 22 and an upper surface 23 opposite to thelower surface, each display pixel Pix comprising:

an electronic circuit 20, called control circuit hereafter, comprisinglower surface 22 and an upper surface 24 opposite to lower surface 22,surfaces 22, 24 being preferably parallel, lower surface 22 being bondedto electrode layer 18, for example, via a bonding material;

optoelectronic circuits 26 bonded to upper surface 24 of electroniccircuit 20, three optoelectronic circuits 26 per display pixels Pixbeing shown in FIG. 2 , each optoelectronic circuit 26 comprising atleast one light-emitting diode, not shown;

an electrically-insulating portion 28 covering optoelectronic circuits26 and covering upper surface 24 of control circuit 20 betweenoptoelectronic circuits 26;

electrically-conductive elements 30 crossing insulating portion 28,coming into contact with optoelectronic circuits 26 and upper surface 24of control circuit 20;

an electrically-insulating layer 32 covering electrode layer 18 betweendisplay pixels Pix and covering the lateral sides of electronic circuits20 and possible of insulating portions 28; and

a second electrode layer 34 comprising an electrically conductive layerat least partially transparent to the radiations emitted by thelight-emitting diodes, conductive layer 34 covering insulating layer 32and insulating portions 28 and being in contact with the conductiveelements 30 of each display pixel Pix.

An encapsulation layer, not shown, may cover conductive layer 34.

When lower surface 22 of electronic circuit 20 is bonded to electrodelayer 18 by a bonding material, the bonding material is preferablyelectrically conductive. As a variation, a bonding material which is notelectrically conductive, for example, arranged at the periphery of lowersurface 22 of electronic circuit 20, may be used.

According to an embodiment, each optoelectronic circuit 26 comprises atleast one light-emitting diode. In the case where optoelectronic circuit26 comprises two or more than two light emitting diodes, all thelight-emitting diodes of optoelectronic circuit 26 preferably emit alight radiation substantially at the same wavelength.

Each light-emitting diode may correspond to a so-called two-dimensionallight-emitting diode comprising a stack of substantially planarsemiconductor layers including the active area. Each light-emittingdiode may comprise at least one three dimensional light-emitting diodehaving a radial structure comprising a semiconductor shell covering athree-dimensional semiconductor element, particularly a microwire, ananowire, a cone, a frustum, a pyramid, or a truncated pyramid, theshell being formed of a stack of non-planar semiconductor layersincluding the active area. Examples of such light-emitting diodes aredescribed in patent application US2014/0077151 and US2016/0218240. Eachlight-emitting diode may comprise at least one three-dimensionallight-emitting diode having an axial structure where the shell islocated in the axial extension of the semiconductor element.

For each display pixel Pix, optoelectronic circuit 26 may be bonded tocontrol circuit by a “flip-chip” type connection. Fusible conductiveelements 36, for example, solder balls or indium balls, which coupleoptoelectronic circuit 26 to control circuit 20 ensure the mechanicalcoupling between optoelectronic circuit 26 and control circuit 20 andfurther ensure the electric connection of the light-emitting diode orthe light-emitting diodes of optoelectronic circuit 26 to controlcircuit 20. According to another embodiment, each optoelectronic circuit26 may be bonded to control circuit 20 by direct bonding.

According to an embodiment, each display pixel Pix comprises at leasttwo types of optoelectronic circuits 26. The optoelectronic circuit 26of the first type is capable of emitting a first radiation at a firstwavelength and the optoelectronic circuit 26 of the second type iscapable of emitting a second radiation at a second wavelength. Accordingto an embodiment, each display pixel Pix comprises at least three typesof optoelectronic circuits 26, the optoelectronic circuit 26 of thethird type being capable of emitting a third radiation at a thirdwavelength. The first, second, and third wavelengths may be different.

According to an embodiment, the first wavelength corresponds to bluelight and is within the range from 430 nm to 490 nm. According to anembodiment, the second wavelength corresponds to green light and iswithin the range from 510 nm to 570 nm. According to an embodiment, thethird wavelength corresponds to red light and is within the range from600 nm to 720 nm.

According to an embodiment, each display pixel Pix comprises anoptoelectronic circuit 26 of a fourth type, the optoelectronic circuit26 of the fourth type being capable of emitting a fourth radiation at afourth wavelength. The first, second, third, and fourth wavelengths maybe different. According to an embodiment, the fourth wavelengthcorresponds to yellow light and is in the range from 570 nm to 600 nm.According to another embodiment, the fourth radiation corresponds to aradiation in close infrared, particularly at a wavelength between 700 nmand 980 nm, to an ultraviolet radiation, or to white light.

Each optoelectronic circuit 26 may comprise a semiconductor substratehaving the light-emitting diode or the light-emitting diodes restingthereon. The semiconductor substrate for example is a substrate made ofsilicon, of germanium, of silicon carbide, of a III-V compound such asGaN or GaAs, a ZnO substrate, or a sapphire substrate. According toanother embodiment, it is possible for each optoelectronic circuit 26 tocomprise no substrate. A mirror layer may then be arranged on the lowersurface of optoelectronic circuit 26 in contact with the light-emittingdiode or the light-emitting diodes. According to an embodiment, themirror layer is capable of at least partly reflecting the radiationemitted by the light-emitting diodes.

Each control circuit 20 may comprise electronic components, not shown,particularly transistors, used to control the light-emitting diodes.Each control circuit 26 may comprise a semiconductor substrate havingthe electronic components formed inside thereof and/or on top thereof.Lower surface 22 of control circuit 20 may then correspond to the rearsurface of the substrate opposite to the front surface of the substrateon the side of which the electronic components are formed. Thesemiconductor substrate is, for example, a substrate made of silicon,particularly, of single-crystal silicon.

Preferably, optoelectronic circuits 26 only comprise light-emittingdiodes and elements of connection of the light emitting diodes andcontrol circuits 20 comprise all the electronic components necessary tocontrol the light-emitting diodes of optoelectronic circuits 26. As avariation, optoelectronic circuits 26 may also comprise other electroniccomponents in addition to the light-emitting diodes.

Optoelectronic device 10 may comprise from 10 to 10⁹ display pixels Pix.Each display pixel Pix may occupy in top view a surface area in therange from 1 μm² to 100 mm². The thickness of each display pixel Pix maybe in the range from 100 μm to 10 mm. The thickness of each electroniccircuit 20 may be in the range from 1 μm to 2,000 μm. The thickness ofeach optoelectronic circuit 26 may be in the range from 0.2 μm to 1,000μm.

Support 12 may be made of an electrically-insulating material, forexample, comprising a polymer, particularly an epoxy resin, and inparticular the FR4 material used for the manufacturing of printedcircuits, or of a metallic material, for example, aluminum. Thethickness of support 12 may be in the range from 100 μm to 10 mm.

Conductive layer 18 preferably corresponds to a metal layer, forexample, aluminum, silver, copper, or zinc. The thickness of conductivelayer 18 may be in the range from 0.5 μm to 1,000 μm.

Each insulating portion 28 may be made of a dielectric material, forexample, of silicon oxide (SiO₂), of silicon nitride (Si_(x) N_(y),where x is approximately equal to 3 and y is approximately equal to 4,for example, Si₃N₄), of silicon oxynitride (SiO_(x)N_(y), where x may beapproximately equal to ½ and y may be approximately equal to 1, forexample, Si₂ON₂), of aluminum oxide (Al₂O₃), or of hafnium oxide (HfO₂).The maximum thickness of each insulating portion 28 may be in the rangefrom 0.5 μm to 1,000 μm.

Each conductive element 30 may be made of a material selected from thegroup comprising copper, titanium, nickel, gold, tin, aluminum, andalloys of at least two of these compounds.

Insulating layer 32 may be made of a dielectric material, for example,of silicon oxide (SiO₂), of silicon nitride (Si_(x)N_(y), where x isapproximately equal to 3 and y is approximately equal to 4, for example,Si₃N₄), of silicon oxynitride (SiO_(x)N_(y), where x may beapproximately equal to ½ and y may be approximately equal to 1, forexample, Si₂ON₂), of aluminum oxide (Al₂O₃), or of hafnium oxide (HfO₂).The thickness of insulating layer 32 may be in the range from 0.02 μm to1,000 μm. Preferably, insulating layer 32 is opaque. Insulating layer 32may correspond to a white resin, to a black resin, or to a transparentresin filled, particularly, with titanium oxide particles.

Conductive layer 34 is capable of letting through the electromagneticradiation emitted by the light-emitting diodes. The material formingconductive layer 34 may be a transparent conductive material such asindium tin oxide (ITO), aluminum or gallium zinc oxide, or graphene. Theminimum thickness of electrically-conductive layer 34 on display pixelsPix may be in the range from 0.1 μm to 1,000 μm.

The encapsulation layer may be made of an at least partially transparentinsulating material. The encapsulation layer may be made of an at leastpartially transparent inorganic material. As an example, the inorganicmaterial is selected from the group comprising silicon oxides of SiO_(x)type, where x is a real number between 1 and 2 or SiO_(y)N_(z), where yand z are real numbers between 0 and 1, and aluminum oxides, forexample, Al₂O₃. The encapsulation layer may be made of an at leastpartially transparent organic material. As an example, the encapsulationlayer is a silicone polymer, an epoxide polymer, an acrylic polymer, ora polycarbonate.

According to an embodiment, in operation, a voltage V_(E) is appliedbetween electrode layers 34 and 18 for the supply of display pixels Pix,particularly of the light-emitting diodes of optoelectronic circuits 26of display pixels Pix.

FIG. 3 shows an equivalent electric diagram of the display pixel Pixshown in FIGS. 1 and 2 . A first electrode, for example, the cathode, ofeach light-emitting diode LED is connected to the control circuit 20 ofdisplay pixel Pix while the second electrode of each light-emittingdiode LED, for example, the anode, is connected to electrode layer 34.Control circuit 20 is connected between electrode layers 18 and 34 andreceives voltage V_(E). Circuit controls the light-emitting diodes ofoptoelectronic circuits 26.

FIG. 4A is a view similar to FIG. 1 of another embodiment of anoptoelectronic device 37 comprising all the elements of optoelectronicdevice 10, with the difference that insulating layer 32 is not presentand that electrode layer 34 rests on a substrate 38. A method ofmanufacturing optoelectronic device 37 comprises forming electrode layer18 on support 12, assembling display pixels Pix on electrode layer 18,forming electrode layer 34 on substrate 38, and then hybridizing displaypixels Pix on electrode layer 34. Support 12 and substrate 38 may beflexible, which enables to manufacture a flexible optoelectronic device37.

FIG. 4B is a view similar to FIG. 1 of another embodiment of anoptoelectronic device 40 comprising all the elements of optoelectronicdevice 10, with the difference that, for each display pixel Pix,optoelectronic circuits 26 are integrated in a single optoelectroniccircuit 42 covering upper surface 24 of the control circuit 20 ofdisplay pixel Pix and bonded to the upper surface 24 of control circuit20, for example, by fusible conductive elements 36. Each optoelectroniccircuit 42 comprises opposite lower and upper surface 44, 46, preferablyparallel, lower surface 44 of optoelectronic circuit 42 being bonded tothe upper surface 24 of control circuit 20. Optoelectronic circuit 42comprises at least one through vertical connection 48 or TSV (throughsilicon via) formed for example in a portion 47 of optoelectroniccircuit 42, which couples upper surface 46 to lower surface 44 and whichis electrically insulated from the rest of optoelectronic circuit 42.Portion 47 may be made of an electrically-insulating material or of asemiconductor material. In this last case, TSV 48 is surrounded with anelectrically-insulating layer. The upper surface 46 of eachoptoelectronic circuit 42 is covered with insulating portion 28.Insulating portion 28 is crossed by an electrically-conductive element30 which is in contact with TSV 48. According to another embodiment, thepower supply of control circuit 20 is achieved with other means than TSV48.

According to an embodiment, each TSV 48 may comprise a core made of anelectrically-conductive material, for example, polysilicon, tungsten,copper, aluminum, or a refractory metallic material, surrounded with anelectrically-insulating layer.

Each optoelectronic circuit 42 comprises at least one firstlight-emitting diode capable of emitting the first radiation at thefirst wavelength and a second light-emitting diode capable of emittingthe second radiation at the second wavelength. Each optoelectroniccircuit 42 may further comprise at least one third light-emitting diodecapable of emitting the third radiation at the third wavelength.

FIG. 5 shows an equivalent electric diagram of display Pix shown in FIG.3 in the case where each optoelectronic circuit 42 comprises threelight-emitting diodes. In this embodiment, the two electrodes of eachlight-emitting diode LED of optoelectronic circuit 42 are connected tocontrol circuit 20 of display pixel Pix. Control circuit 20 is connectedbetween electrode layers 18 and 34 and receives voltage V_(E). Circuit20 controls the light emitting diodes, LED, of optoelectronic circuit26.

In the present embodiment, conductive layer 18 is in contact with allthe display pixels Pix of optoelectronic circuit 10, 40, and conductivelayer 34 is in contact with all the display pixels Pix of optoelectronicdevice 10, 40.

An embodiment of a method of manufacturing optoelectronic device 10 or40 comprises manufacturing display pixels Pix and separately installingeach display pixel Pix on electrode layer 18. According to anembodiment, electrode layers 18 and 34 being common to all displaypixels Pix, the connection of display pixels Pix is simplified and it isnot necessary for the placing of each display pixel Pix on electrodelayer 18 to be performed with a high accuracy. This advantageouslyenables to implement faster techniques at decreased costs to arrangedisplay pixels Pix on electrode layer 18. Further, since thelight-emitting diodes are previously assembled on electronic circuit 20of display pixel Pix, the number of transfers to be performed during theassembly of optoelectronic device 10 or 40 is decreased. In the presentembodiment, each display pixel Pix may comprise a memory having anidentifier of the pixel stored therein. The manufacturing method maycomprise a calibration phase where the position of each display pixelPix is recovered according to its identifier. In operation, data maythen be transmitted to the pixels according to their identifier.

FIG. 6 shows a simplified top view of optoelectronic device 10 or 40illustrating the fact that it is possible for display pixels Pix not tobe very accurately arranged, for example, perfectly aligned in rows andin columns and that certain display pixels Pix may be inclined withrespect to the directions of the rows and of the columns.

In the previously-described embodiments, electrode layer 18 is connectedto all the display pixels Pix and appears in the form of anuninterrupted layer extending over most of or even all of support 12.

For each display pixel Pix, control circuit 20 is capable of receivingcontrol signals and of controlling, from the received control signals,the light-emitting diodes of the display pixel, particularly the shade,the saturation, and the brightness of the light emitted by the displaypixel.

According to an embodiment, the control signals may be transmitted tothe control circuits 20 of display pixels Pix by a modulation of voltageV_(E).

FIG. 7 very schematically shows a processing unit 49 receiving controlsignals COM and capable of supplying optoelectronic device 10 and 40with a voltage V_(E) for powering display pixels Pix, which is modulatedwith control signals COM. Processing unit 49 may correspond to adedicated circuit or may comprise a processor, for example, amicroprocessor or a microcontroller, capable of executing instructionsof a computer program stored in the memory.

The control circuit 20 of each display pixel Pix may extract controlsignals COM by demodulation of voltage V_(E). Control circuit 20 canthen determine whether control signals COM are addressed thereto. As anexample, an identifier may be associated with each display pixel Pix andthe control signals COM obtained by demodulation of voltage V_(E) maycomprise the identifier of the display pixel for which the controlsignals are intended.

Advantageously, an active addressing of display pixels Pix may beperformed. Indeed, each control circuit 20 may control the maintainingof the display properties, particularly the shade, the saturation, andthe brightness, of the display pixel until it receives new controlsignals.

FIG. 8A shows a simplified top view of another embodiment of anoptoelectronic device 50 comprising all the elements of optoelectronicdevice 10 or 40, where electrode layer 18 is divided into parallelelectrically-conductive strips 52 extending on support 12, three strips52 being shown as an example in FIG. 8 . As least one row of displaypixels Pix is distributed on each conductive strip. Preferably, aplurality of rows of display pixels Pix are distributed on eachconductive strip 52, three rows of display pixels Pix being shown perconductive strip 52 as an example in FIG. 8 .

According to another embodiment, electrode layer 18 and/or electrodelayer 34 may be divided into separate electrode portions. According toanother embodiment, electrode layer 34 may also be divided into parallelelectrically-conductive strips. When electrode layers 18 and 34 are eachdivided into strips, the strips of electrode layer 18 preferably havesubstantially the same dimensions as the strips of electrode layer 34and each strip of electrode layer 34 substantially covers a single oneof the strips of electrode layer 18. According to another embodiment,one of electrodes 18 or 34 may be common to display pixels Pix while theother electrode 18 or 34 is divided into parallelelectrically-conductive strips. In the embodiment where electrode layers18, 34 are divided into stacked strips sandwiching assemblies of displaypixels, different control signals may be transmitted in parallel bymodulating voltage V_(E) differently for each assembly of displaypixels. This enables to transmit in parallel the control signals foreach assembly of display pixels Pix. This enables to decrease themodulation frequency of the electromagnetic radiation and/or to increasethe rate of transmitted data.

FIG. 8B is a partial simplified top view of another embodiment of anoptoelectronic device 55 where electrode layer 18 is divided intoconductive strips 56 extending along the row direction and whereelectrode layer 34 is divided into conductive strips 58 extending alongthe column direction, and called columns electrodes. At least onedisplay pixel Pix is arranged at the intersection, in top view, betweeneach row electrode 56 and each column electrode 58 and is connected torow electrode 56 and to column electrode 58. As an example, in FIG. 8B,three display pixels Pix are provided at the intersection, in top view,of each row electrode 56 and each column electrode 58 and form a pixelof the image to be displayed. When a plurality of display pixels Pix areprovided for each pixel of the image to be displayed, this enables tohave a redundancy in the case where one of display pixels Pix would bedefective.

FIG. 9 is a view similar to FIG. 1 of another embodiment of anoptoelectronic device 60 comprising all the elements of optoelectronicdevice 10 and further comprising a stack of a first layer 62 and of asecond layer 64 covering electrode layer 34. Layer 62 is made of amaterial having a refraction index greater than the refraction index ofthe material forming layer 64. Layers 62 and 64 are at least partiallytransparent to the radiations emitted by display pixels Pix. Layer 64 isfor example made of glass, of SiO₂, of Al₂O₃, of HfO₂, of an organicmaterial, for example, a polymer, particularly poly(methyl methacrylate)(PMMA). Layer 62 for example corresponds to an air film. Layer 64 formsa waveguide for an electromagnetic radiation 66, for example, in thevisible range or outside of the visible range, preferably in awavelength range between the infrared and ultraviolet range.Optoelectronic device 60 comprises an optoelectronic circuit 68 capableof emitting such a radiation 66 in layer 64. Optoelectronic circuit 68may be located at the periphery of layer 64 and may emit radiation 66 inlayer 64 from the lateral edge thereof. The infrared radiation ismodulated to transport the previously-described control signals.According to an embodiment, optical coupling means 70 are providedbetween each display pixel Pix and waveguide 64 so that a fraction 72 ofthe radiation 66 guided in waveguide 64 escapes at the level of eachdisplay pixel Pix via coupling means 70. As an example, coupling means70 correspond to a texturing provided on layer 64 and/or on layer 62opposite each display pixel Pix to ensure the optical coupling betweeneach display pixel Pix and layer 64. Coupling means 70 for examplecorresponds to a diffraction grating enabling to reflect part of theelectromagnetic radiation propagating in waveguide 64 towards theassociated display pixel Pix.

Each display pixel Pix comprises at least one sensor 74 capable ofdetecting the radiation emitted by optoelectronic circuit 68, forexample, a photodiode or a photoresistor, the sensor supplying controlcircuit 20 with an electric signal for example representative of theintensity of radiation 72 received by display pixel Pix. Control circuit20 is connected to the sensor and is capable of extracting the controlsignals based on the measurement signal supplied by the sensor.

According to an embodiment, the same electromagnetic radiationtransporting the control signals is transmitted to all display pixelsPix. According to another embodiment, a plurality of waveguides may beprovided, each waveguide being associated with an assembly of displaypixels. According to another embodiment, optical continuity break areasmay be formed in the waveguide to be able to address different groups ofpixels.

FIG. 10 is a partial simplified top view of another embodiment of anoptoelectronic device 80 comprising separate waveguides 82, or a singlewaveguide having optical discontinuities, each covering an assembly ofdisplay pixels, not shown. Optoelectronic device 80 further comprisesoptoelectronic circuits 84, each capable of emitting in the associatedwaveguide 82 an electromagnetic radiation in the non-visible range. Thisenables to transmit in parallel the control signals for each assembly ofdisplay pixels Pix. This enables to decrease the modulation frequency ofthe electromagnetic radiation and/or to increase the rate of transmitteddata.

FIG. 11 is a partial simplified top view of another embodiment of anoptoelectronic device 90 comprising all the elements of the device 80,each separate waveguide 82 covering at least one row of display pixels.

In the present embodiment, electrode layer 34 or electrode layer 18 isdivided into conductive strips 92 extending along the column direction.Each conductive strip 92 is coupled to the display pixels of at leastone pixel column.

An embodiment of a display pixel control method comprises a phase ofselection of a display pixel or of a group of display pixels viaelectrodes 18, 92, followed by a phase of data transmission to some ofthe display pixels selected by one of waveguides 82. The selection phasemay be performed by taking the conductive strip 92 coupled to thedisplay pixels to be selected to a first potential while the otherconductive strips 92 are maintained at a second potential different fromthe first potential. Only the display pixels which are selected areactive and are capable of processing data transmitted by anelectromagnetic radiation. The other display pixels are inactive andignore the data which are transmitted by the radiation. The radiationtransporting the data is then emitted into the waveguide 82 which coversthe pixels of interest. Only the display pixels which have been selectedand which are covered with waveguide 82 will process the data obtainedby the detection of the radiation transmitted by waveguide 82.

According to an embodiment, each conductive strip 92 is coupled to thedisplay pixels of a single column of display pixels and each waveguide82 only covers one row of display pixels. The previously-describedcontrol method then enables to only select and transmit data to a singledisplay pixel.

FIG. 12 is a partial simplified top view of another embodiment of anoptoelectronic device 100 where electrode layer 18 is divided intoconductive strips 102 extending along the row direction and called rowelectrodes, each conductive strip 102 being coupled to the displaypixels Pix of a pixel row and where electrode layer 34 is divided intoconductive strips 104 extending along the column direction and calledcolumn electrodes, each conductive strip 104 being coupled to thedisplay pixels Pix of a pixel column.

As shown in FIG. 12 , the width of each conductive strip 102 is greaterthan the dimension of display pixel Pix measured along the columndirection and the width of each conductive strip 104 is greater than thedimension of display pixel Pix measured along the row direction.Thereby, for each row, it is possible for the display pixels Pixbelonging to the row not to be perfectly aligned. Similarly, for eachcolumn, it is possible for the display pixels Pix belonging to thecolumn not to be perfectly aligned.

An embodiment of a method of controlling a display pixel Pix comprises aphase of selection of the display pixel followed by a phase of datatransmission to display pixel Pix.

FIG. 13 is a timing diagram respectively of potentials Vpix+ and Vpix−respectively applied to the column and row electrodes coupled to adisplay pixel to be controlled and FIG. 14 is a timing diagram ofvoltage sig seen between the power supply terminals of the display pixelto be controlled.

According to an embodiment, optoelectronic circuit 100 is capable ofvarying the potential of each row electrode between two values V0 andV1, V1 being greater than V0, and of varying the potential of eachcolumn electrode between two values V2 and V3, V3 being greater than V2and V2 being greater than V1. The difference between V3 and V2 may beequal to the difference between V1 and V0.

According to an embodiment, the control method comprises a phase Si ofselection of a display pixel to be controlled, followed by a phase S2 ofdata transmission to the selected display pixel.

Phase S1 comprises taking the row electrode coupled to the display pixelto be controlled to V0, the other row electrodes being left at V1, andtaking the column electrode coupled to the display pixel to becontrolled to V3, the other row electrodes being left at V2. The displaypixel to be controlled then sees a voltage equal to V3-V0, while theother display pixels of the same row see a voltage equal to V2-V0, theother display pixels of the same column see a voltage equal to V3-V1 andthe other display pixels of the other rows and columns see a voltageequal to V2-V1. All the display pixels other than the display pixel tobe controlled see a voltage smaller than V3-V0.

Phase S2 comprises varying the potential of the column electrode of thedisplay pixel to be controlled between V2 and V3 while leaving the rowelectrode of the display pixel to be controlled at V1. Thereby, thevoltage seen by the display pixel to be controlled varies like thepotential of the column electrode.

Each display pixel is capable of detecting whether, at phase S1, thepower supply voltage which is applied thereto is greater than athreshold. When a display pixel detects that, at phase S1, the powersupply voltage which is applied thereto is greater than a threshold, itis capable of processing the data, which are then transmitted duringphase S2. When a display pixel detects that, at phase S1, the powersupply voltage which is applied thereto is smaller than the threshold,it does not process the data, which are then transmitted thereto duringphase S2.

The present embodiment enables to select a display pixel whilemaintaining the power supply of the other display pixels. The presentembodiment further enables to transmit data to a single display pixel ofan array of display pixels. Advantageously, all the display pixels ofthe array may correspond to identical optoelectronic devices. Thisenables to simplify the design of the display pixels and the assembly ofthe display pixels. The present embodiment further enables tosimultaneously transmit data to a plurality of display pixels, or evento simultaneously transmit data to all the display pixels. Further, thefact for the potential of one of the electrodes to remain constantduring phase S2 advantageously enables the display pixel to have aconstant potential reference during phase S2, which simplifies theprocessing of the signals by the display pixel.

The data transmitted during phase S2 may be binary data and/or analogdata. The transmitted data may be modulated. It may be a frequency,amplitude, phase modulation, or a pulse width modulation.

As an example, in FIGS. 13 and 14 , phase S2 successively comprises asub-phase Scom corresponding to the transmission of binary data, a phaseSR corresponding to the transmission of a control signal for a firstdisplay sub-pixel, for example, the red display sub-pixel, a phase SGcorresponding to the transmission of a control signal for a seconddisplay subpixel, for example the green display sub-pixel, and a phaseSB corresponding to the transmission of a control signal for a thirddisplay sub-pixel, for example, the blue display sub-pixel. As avariation, sub-phase Scom may be omitted.

According to an embodiment, each sub-phase SR, SG, and SB comprisestransmitting a voltage pulse having a duration representative of thedesired duration of activation of the considered display sub-pixel.

FIG. 15 shows an equivalent electric diagram of an embodiment of displaypixel Pix.

Display pixel Pix is coupled to one of the column electrodes 104 whichis at potential Vpix+ and to one of the row electrodes 102 which is atpotential Vpix−.

Display pixel Pix comprises a processing unit CM (Signal Processor), aunit CR for controlling a first display sub-pixel (Red Pixel), forexample, the red display sub-pixel, a unit CG for controlling a seconddisplay sub-pixel (Green Pixel), for example, the green displaysub-pixel, and a unit CB for controlling a third display sub-pixel (BluePixel), for example, the blue display sub-pixel. The electroniccomponents of processing unit CM are located at the level of controlcircuit 20. The electronic components of units CR, CG, CB may be locatedat the level of control circuit 20 and/or at the level of optoelectroniccircuits 26.

Each unit CM, CR, CG, and CB is coupled to the column and row electrodes102, 104 associated with potentials Vpix+ and Vpix− for their electricpower supply. Control circuit CM receives the potential values Vpix+ andVpix− and a signal end as input signals and outputs three binary signalsdata, write, and clear. According to an embodiment, units CR, CG, and CBare identical and each unit CR, CG, and CB comprises three inputs writecapacitor, write enable, and clear pixel and an output write done. As avariation, unit CB may be different from units CR and CG and maycomprise no output write done. Inputs write capacitor of each unit CR,CG, and CB each receive signal data. Inputs clear pixel of each unit CR,CG, and CB each receive signal clear. Input write enable of unit CRreceives signal write. Input write enable of unit CG is coupled tooutput write done of unit CR and input write enable of unit CB iscoupled to output write done of unit CG. In the embodiment illustratedin FIG. 15 , output write done of unit CB supplies the signal endreceived by unit CM.

FIG. 16 shows an equivalent electric diagram of an embodiment of unitCR, where units CG and CB may be identical.

According to an embodiment, unit CR comprises a light-emitting diode LEDhaving its anode coupled to the electrode at potential Vpix+ and havingits cathode coupled to a control terminal among the drain or the sourceof a MOS transistor T1 and having its other control terminal coupled tothe electrode at potential Vpix−. Unit CR further comprises a capacitorC1 having an electrode coupled to the gate of transistor T1 and havingits other electrode coupled to the electrode at potential Vpix−. Unit CRfurther comprises a MOS transistor T2 having a control terminal amongthe drain or the source coupled to the gate of transistor T1 and havingits other control terminal coupled to the electrode at potential Vpix−.The gate of transistor T2 is coupled to input clear pixel. Unit CRfurther comprises a three-input AND logic gate AND1 having two inputscorresponding to inputs write enable and write capacitor of unit CR.Logic gate AND1 supplies a control signal enable to a current source CShaving a terminal coupled to the electrode at potential Vpix+ and havingits other terminal coupled to the gate of transistor T1. Unit CR furthercomprises an RS flip-flop RS1 having its S input, sensitive to fallingedges, receiving signal enable, having its R input coupled to inputclear pixel of unit CR, and having its Q output coupled to the thirdinput of logic gate AND1. The Q output of flip-flop RS1 is coupled tooutput write done of unit CR.

FIG. 17 shows a timing diagram of signals during a cycle of control ofthe display pixel of FIG. 15 . Call t0, t1, t2, t3, t4, t5, t6, and t7successive times. Output write enable of unit CR supplies signal RedDone. Output write enable of unit CG supplies signal Green Done. Outputwrite enable of unit CB supplies signal Blue Done.

Signals Red Cap, Green Cap, and Blue Cap respectively correspond to thevoltages across capacitors C1 respectively of units CR, CG, and CB.Signal sig corresponds to the difference between potentials Vpix+ andVpix−. Signal sig may take three discrete values “0”, “1”, and “2”.

In the present embodiment, signal data is equal to signal sig outside ofthe selection phase and signal write is set to “1” during the phases ofcontrol of the display sub-pixels.

At time t0, signals Red Done, Green Done, and Blue Done are at “1”,signal sig is at “0”, and signal clear is at “0”. At time t1, signal sigswitches from “0” to “2”. Unit CM detects that the display pixel isselected and sets signal clear to “1”. At time t2, signal sig switchesto “0”. Unit CM then sets signal write to “1” and signal clear to “0”.This initializes flip-flops RS1 of units CR, CG, and CB, sets signalsRed Done, Green Done, and Blue Done to “0”, and empties capacitors C1 ofunits CR, CG, and CB, setting voltages Red Cap, Green Cap, and Blue Capto 0. At time t3, the phase of control of the red display sub-pixelstarts. In the present embodiment, the red display sub-pixel isactivated and signal sig switches to “1”. Signal data is equal to signalsig so that capacitor C1 of unit CR is charged by current source CSuntil time t4 at which signals sig and data switch to “0”. Signal RedDone then switches to “1”. At time t5, the phase of control of the greendisplay sub-pixel starts. In the present embodiment, the green displaysub-pixel is not activated and signal sig switches to “1” for a veryshort time. Capacitor C1 of unit CG is not substantially charged andsignal Green Done then switches to “1”. At time t6, the phase of controlof the blue display sub-pixel starts. In the present embodiment, theblue display sub-pixel is activated and signal sig switches to “1”.Signal data is equal to signal sig so that capacitor C1 of unit CR ischarged by current source CS until time t7 at which signals sig and dataswitch to “0”. Signal Blue Done then switches to “1”.

FIG. 18 shows an equivalent electric diagram of another embodiment ofunit CM adapted to the case where signal end is supplied by output writeof unit CG, units CR, CG for example corresponding to the electricdiagram shown in FIG. 20 described hereafter and unit CB for examplecorresponding to the electric diagram shown in FIG. 21 describedhereafter. In the present embodiment, during transmission phase S2,signal data is equal to signal sig delayed by a given duration ΔT andsignal write is equal to signal sig.

Unit CM comprises a block start detector comprising an input s+ coupledto the electrode at potential Vpix+ and an input s− coupled to theelectrode at potential Vpix− and supplying a binary signal start. Blockstart detector is capable of detecting that signal sig, whichcorresponds to the voltage between inputs s+ and s−, switches to “2” andis capable of setting signal start to “1” when signal sig switches backto “0”.

Unit CM comprises a block data extractor comprising an input s+ coupledto the electrode at potential Vpix+, an input s− coupled to theelectrode at potential Vpix−, and an input enable receiving signalstart. The block supplies signal clear and signal raw_data which isextracted from signal sig, and which for example corresponds to a binaryversion of signal sig outside of the selection phase.

Unit CM comprises a block zero detector receiving signal raw_data andsupplying signal write equal to signal raw_data and supplying signaldata, which is equal to signal raw_data for which the duration of eachpulse at “1” is decreased by duration ΔT, the beginning of each pulsebeing delayed by duration ΔT and the end of each pulse being unmodifiedso that, if the pulse of signal raw_data is shorter than duration ΔT,signal data comprises no corresponding pulse.

FIG. 19 shows a more detailed electric diagram of an embodiment of unitCM shown in FIG. 18 .

Unit CM comprises a first voltage dividing bridge comprising tworesistors R1 and R2 series-assembled between the electrode at potentialVpix+ and the electrode at potential Vpix−. The midpoint of the firstdividing bridge supplies a succession of two inverters INV1 and INV2 inseries, the second inverter INV2 supplying signal start. Unit CMcomprises an RS flip-flop RS2 having its S input receiving signal startand having input R, sensitive to the falling edges, receiving a signalend. Signal end is supplied by output write done of unit CG as describedin FIG. 20 . Unit CM comprises a NOR logic gate NOR1 having its firstinput receiving signal start, having its second input coupled to the Qoutput of flip-flop RS2 and supplying signal enable.

Unit CM comprises a second voltage dividing bridge comprising tworesistors R3 and R4 series-assembled between the electrode at potentialVpix+ and the electrode at potential Vpix−. Unit CM comprises three MOStransistors T3, T4, and T5 series assembled between the electrode atpotential Vpix+ and the electrode at potential Vpix−. Transistor T3 hasa P channel and transistors T4 and T5 have an N channel. The gates oftransistors T3 and T4 receive signal enable. The midpoint of the seconddividing bridge powers the gate of transistor T5.

The source of transistor T3 powers an inverter INV3, which suppliessignal write. Unit CM comprises a two-input AND logic gate AND2 havingits first input receiving signal write. Unit CM comprises a resistor R5assembled between the output of inverter INV3 and the second input ofgate AND2. Unit CM comprises a capacitor C2 having an electrode coupledto the second input of gate AND2 and having its other electrode coupledto the electrode at potential Vpix−. The output of gate AND2 suppliessignal data.

FIG. 20 shows an equivalent electric diagram of an other embodiment ofunit CR, where unit CG may be identical. Unit CR comprises all theelements of the unit shown in FIG. 16 , with the difference that the Sinput of flip-flop RS1 is coupled to input write enable of unit CR andin that it comprises a two-input AND logic gate AND3 having its firstinput receiving the Q signal, having its second input coupled to inputwrite enable, and having its output coupled to output write done.

FIG. 21 shows an equivalent electric diagram of another embodiment ofunit CB. Unit CB comprises all the elements of the unit shown in FIG. 16, with the difference that flip-flop RS1 is not present and thatthree-input logic gate AND1 is replaced with a two input logic gate AND4having its first input coupled to input write capacitor of unit CB andhaving its second input coupled to input write enable of unit CB andsupplying signal enable.

FIG. 22 shows a timing diagram of signals during a cycle of control ofthe display pixel of FIG. 18 . Call t′0, t′1, t′2, t′3, t′4, t′5, t′6,t′7, t′8, and t′9 successive times. Signals Red write enable, Greenwrite enable, and Blue write enable correspond to the signalsrespectively received by inputs write enable of units CR, CG, and CB.

The signals vary at times t′0, t′1, t′2 in the same way as what has beenpreviously described for signals t0, t1, and t2. At time t′3, the reddisplay sub-pixel control phase starts. In the present embodiment, thered display sub-pixel is activated and signal sig switches to “1”.Signal data is equal to signal sig delayed by a duration ΔT so that thecapacitor C1 of unit CR is charged by current source CS from time t′4 totime t′5 at which signals sig, data, and Red write enable switch to “0”.Signal write done of unit CR then becomes equal to signal Red writeenable. At time t′6, the green display sub-pixel control phase starts.In the present embodiment, the green display sub-pixel is not activatedand signal sig switches to “1” for a duration shorter than ΔT. Signalwrite and Green write enable also switch to “1” for this very shortduration. However, signal data remains at “0” so that capacitor C ofunit CG is not charged. Signal write done of unit CR then becomes equalto signal Green write enable. At time t′7, the blue display sub-pixelcontrol phase starts. In the present embodiment, the blue displaysub-pixel is activated and signal sig switches to “1”. Signal data isequal to signal sig delayed by a duration ΔT so that the capacitor C ofunit CB is charged by current source CS from time t′8 to time t′9 atwhich signals sig, data, Red write enable, Green write enable, and Bluewrite enable switch to “0”.

According to an embodiment, the display pixel may be formed with lessthan 150 MOS transistors, 5 resistors, and 4 capacitors. It may thusoccupy a small surface area.

FIG. 23 shows an electric diagram of another embodiment of display pixelPix.

Display pixel Pix is coupled to one of the column electrodes 102 whichis at potential Vpix+ and to one of the row electrodes 104 which is atpotential Vpix−.

Display pixel Pix comprises a level detection unit M1, a rising edgedetector M2, and a counter M3 (Ring Counter), and display sub-pixelcontrol units CR, CG, and CB. The electronic components of units M1, M2,and M3 are located at the level of control circuits 20. The electroniccomponents of units CR, CG, CB may be located at the level of controlcircuit and/or at the level of optoelectronic circuits 26.

Each unit M1, M2, M3, CR, CG, and CB is coupled to the column and rowelectrodes 102, 104 associated with potentials Vpix+ and Vpix− for theirelectric power supply.

Unit M1 receives potential values Vpix+ and Vpix− as input signalsrespectively at inputs V+ and V− and a binary signal Reset and suppliesa binary signal Detect enable and a binary signal Clear. Unit M2receives potential values Vpix+ and Vpix− as input signals respectivelyat inputs V+ and V− and binary signal Detect enable at an input Enableand supplies a binary signal Clock. Unit M3 receives binary signal Clockand supplies three binary signals b0, b1, and b2. The falling edge of b2resets unit M1.

Each unit CR, CG, and CB comprises an input Cap reset and an input Prog.Input Cap reset of each unit CR, CG, and CB receives signal Detectenable. Input Prog of unit CR receives signal b0, input Prog of unit CGreceives signal b1, and input Prog of unit CB receives signal b2.

In the present embodiment, unit M1 is capable of detecting that thedisplay pixel is selected by an increase of signal sig. When a selectionhas been detected, unit M2 detects the rising edges of signal sig. Thecapacitors of units CR, CG, and CB are sequentially charged, theswitching from one unit to another being triggered by a falling edge ofsignal sig. At the beginning of each sequence, the capacitors of unitsCR, CG, and CB are discharged.

FIG. 24 shows an embodiment of unit M3. Unit M3 comprises a successionof four D-type flip-flops with asynchronous /S and /R inputs, D1, D2,D3, and D4. The ck input of each flip-flop D1, D2, and D3 receivessignal Clock. The Q output of flip-flop D1 is coupled to the D input offlip-flop D2, the Q output of flip-flop D2 is coupled to the D input offlip-flop D3, and the Q output of flip-flop D3 is coupled to the D inputof flip-flop D4. The output of flip-flop D1 is at “1” at the setting ofthe counter while the outputs of the other flip-flops are at logic state“0”. Bit b0 corresponds to the signal supplied by the Q output offlip-flop D2, bit b1 corresponds to the signal supplied by the Q outputof flip-flop D3, and bit b2 corresponds to the signal supplied by the Qoutput of flip-flop D4. Signal Clear originating from unit M1 issupplied to inverter INV9 and powers the /S input of flip-flop D1 aswell as the /R inputs of flip-flops D2, D3, and D4.

FIG. 25 shows an embodiment of unit CR. Units CG and CB may have thesame structure. Unit CR has the same structure as unit CR shown in FIG.16 , with the difference that logic gate AND1 and flip-flop RS1 are notpresent, that current source CS is controlled by the signal received atinput Prog of unit CR, and that the gate of transistor T2 is controlledby the signal received at input Cap_reset of unit CR.

FIG. 26 shows a timing diagram of signals during a cycle of control ofthe display pixel of FIG. 23 . Call t″0, t″1, t″2, t″3, t″4, t″5, t″6,t″7, t″8, t″9, t″10, t″11, and t″12 successive times.

At time t″0, signals sig, Cap_reset, detect enable, up, b0, b1, and b2are at “0”. At time t″1, signal sig switches from “0” to “2”. Unit M1detects that the display pixel is selected and sets signal Clear andsignal detect enable to “1”. At time t″2, signal sig switches to “1” andunit M1 switches signal Clear to “0”. At time t″3, red display sub-pixelcontrol phase SR starts. In the present embodiment, the red displaysub-pixel is activated and signal sig switches to “2”. Signal clock isset to “1” from time t″3 to time t″4. Signal b0 is set to “1” at timet″3. At time t″5, signal sig switches to “1”. At time t″6, signal sigswitches to “2”, phase SG of control of the green display sub-pixelstarts while the red sub-pixel control phase is ended. In the presentembodiment, the green display sub-pixel is activated. Signal clock isset to “1” from time t″6 to time t″7. Signal b1 is set to “1” at timet″6. Signal b0 is set to “0” at time t″6. At time t″8, signal sigswitches to “2”, phase SB of control of the display sub-pixel starts. Inthe present embodiment, the blue display sub-pixel is activated. Signalclock is set to “1” from time t″8 to time t″9. Signal b2 is set to “1”at time t″8. Signal b1 is set to “0” at time t″8. At time t″10, signalsig switches to “1”. At time t″11, signal sig is set to “2”. The end ofthe transaction is notified. At time t″11, signal clock is set to “1”and signal b2 is set to “0”, phase SB of control of the blue sub-pixelends. At time t″12, signal sig switches to “1” and then to “0”.

According to an embodiment, the display pixel may be formed with lessthan 150 MOS transistors, 3 resistors, and 4 capacitors. It may thusoccupy a small surface area.

To optimize the data transfer conditions, all the embodiments mightintegrate a function to turn off the pixels in the addressed row orcolumn for the duration of the communication, which would limit the loadto be driven during the data transfer. The addition of such afunctionality may be performed by decreasing potential differentVpix+-Vpix−.

FIGS. 27A to 27H are partial simplified cross-section views ofstructures obtained at successive steps of another embodiment of amethod of manufacturing the optoelectronic device of FIG. 10 shown inFIGS. 1 and 2 .

FIG. 27A shows the structure obtained after the manufacturing of anelectronic circuit 110 comprising a plurality of the desired controlcircuit 20, four control circuits 20 being shown as an example in FIG.27A. The method of manufacturing electronic circuit 110 may compriseconventional steps of an integrated circuit manufacturing method.

FIG. 27B shows the structure obtained after having affixed theoptoelectronic circuits 26 onto electronic circuit 110. The methods ofassembly of optoelectronic circuits 26 on electronic circuit 110 maycomprise soldering operations.

FIG. 27C shows the structure obtained after the deposition of anelectrically-insulating layer 112 covering optoelectronic circuits 26and electronic circuit 110 between optoelectronic circuits 26.Insulating layer 112 is made of the same material as thepreviously-described insulating portions 28. Insulating layer 112 may bemade of SiO₂, SiN, Al₂O₃, ZrO₂, HfO₂ or of any other dielectric materialdeposited by chemical vapor deposition (CVD), plasma-enhanced chemicalvapor deposition (PECV), atomic layer deposition (ALD), or cathodesputtering.

FIG. 27D shows the structure obtained after the forming of conductiveelements 30 in insulating layer 112. Conductive elements 30 may beformed by etching openings in insulating layer 112 stopping onoptoelectronic circuits 26 and/or control circuits 20, by depositing aconductive layer over the entire obtained structure, and by removing theportion of the conductive layer outside of the openings.

FIG. 27E shows the structure obtained after the sawing of electroniccircuit 110 and of insulating layer 112 to delimit display pixels Pix.

FIG. 27F shows the structure obtained after having affixed displaypixels Pix to electrode layer 18 which has been previously deposited onsupport 12. As an example, each display pixel Pix may be affixed toelectrode layer 18 by molecular bonding or via a bonding material,particularly, an electrically-conductive epoxy glue.

FIG. 27G shows the structure obtained after having formed insulatinglayer 32 on display pixels Pix and on electrode layer 18 between displaypixels Pix. Insulating layer 32 may be SiO₂, SiN, Al₂O₃, ZrO₂, HfO₂ orany other dielectric material.

FIG. 27H shows the structure obtained after having removed insulatinglayer 32 from the top of each display pixel Pix. According to anembodiment, the removal may be carried out by chem.-mech. polishing(CMP) with a stop on insulating portions 28. According to anotherembodiment, this may be obtained by chemical etching of insulating layer32. According to another embodiment, the removal may be carried out by aso-called lift-off method comprising the deposition of a sacrificiallayer at the top of each display pixel Pix before the deposition ofinsulating layer 32 and, after the deposition of insulating layer 32,the removal of the sacrificial layer and of the portion of insulatinglayer 32 covering the sacrificial layer.

FIG. 27I shows the structure obtained after the forming of electrodelayer 34. Electrode layer 34 may be made of TCO (Transparent ConductiveOxide) deposited by CVD, PECVD, ALD, cathode sputtering, or evaporation.

FIGS. 28A to 28D are partial simplified cross-section views ofstructures obtained at successive steps of another embodiment of amethod of manufacturing the optoelectronic device shown in FIG. 4B.

FIG. 28A shows the structure obtained after the forming of anoptoelectronic circuit 90 comprising a plurality of optoelectroniccircuits 42, three optoelectronic circuits 42 being shown as an examplein FIG. 27A. As an example, in FIG. 28A, each optoelectronic circuit 42is shown as comprising two optoelectronic circuits 26 separated byportion 47.

FIG. 28B shows the structure obtained after the forming of TSVs 48crossing optoelectronic circuits 64. Each TSV 48 may be formed byetching an opening crossing optoelectronic circuit 90. This opening mayhave a circular or rectangular cross-section. The etching may be a deepreactive ion etching (DRIE). An insulating layer is then deposited onthe walls of the opening. The insulating layer is for example formed byconformal deposition by PECVD or by conformal deposition of aninsulating polymer. The insulating layer has a thickness in the rangefrom 10 nm to 5,000 nm, for example, approximately 3 μm. The filling ofthe TSV may then be carried out by electrolytic copper deposition.

FIG. 28C shows the structure obtained after the deposition of aninsulating layer 92 on optoelectronic circuit 90. Insulating layer 92 ismade of the same material as the previously-described insulatingportions 28. Insulating layer 92 may be deposited by CVD, PECVD, ALD, orcathode sputtering.

FIG. 28D shows the structure obtained after the forming of conductiveelements 30 in insulating layer 92.

The subsequent steps of the method may be the same as those previouslydescribed in relation with FIGS. 27E to 27I.

Various embodiments with different variations have been describedhereabove. It should be noted that those skilled in the art may combinevarious elements of these various embodiments and variations withoutshowing any inventive step. As an example, the electric diagram shown inFIG. 3 may be implemented with the structure of device 40 shown in FIG.4B and the electric diagram shown in FIG. 5 may be implemented with thestructure of device 10 shown in FIGS. 1 and 2 .

The invention claimed is:
 1. An optoelectronic device comprising: asupport; at least one first electrically-conductive layer covering thesupport; display pixel circuits comprising first and second oppositesurfaces and bonded to the first electrically-conductive layer, eachdisplay pixel circuit comprising an electronic circuit comprising thefirst surface and a third surface opposite to the first surface, and atleast one optoelectronic circuit bonded to the third surface andcomprising at least one light-emitting diode, at least one of theelectrodes of the light-emitting diode being connected to the electroniccircuit by the third surface, the first surface of each of at least twodisplay pixel circuits among the display pixel circuits being bonded tothe at least one first electrically-conductive layer; at least onesecond electrically-conductive layer covering at least two display pixelcircuits among the display pixel circuits and electrically coupled, onthe side of the second surface, to the electronic circuit of each ofsaid at least two display pixel circuits covered by said at least onesecond electrically-conductive layer.
 2. The optoelectronic device ofclaim 1, further comprising an electrically-insulating layer coveringthe first electrically-conductive layer between the display pixelcircuits.
 3. The optoelectronic device of claim 2, wherein theelectrically-insulating layer covers the lateral sides of the displaypixel circuits.
 4. The optoelectronic device of claim 1, wherein each ofsaid at least two display pixel circuits covered by said at least onesecond electrically-conductive layer further comprises anelectrically-insulating portion covering the electronic circuit and theoptoelectronic circuit and at least one electrically-conductive elementcrossing the electrically-insulating portion and electrically coupled tothe second electrically-conductive layer and to the optoelectroniccircuit or to the electronic circuit.
 5. The optoelectronic device ofclaim 4, wherein, for each of said at least two display pixel circuitscovered by said at least one second electrically-conductive layer, theoptoelectronic circuit comprises a through connection electricallyinsulated from the rest of the optoelectronic circuit and electricallycoupled to the electronic circuit and to the conductive element.
 6. Theoptoelectronic device of claim 1, comprising at least two first separateelectrically-conductive layers and covering the support, display pixelcircuits among the display pixel circuits being bonded to the firstelectrically-conductive layers, and at least two secondelectrically-conductive layers covering display pixel circuits among thedisplay pixel circuits and being electrically coupled to the electroniccircuits of the display pixel circuits covered by the secondelectrically-conductive layers.
 7. The optoelectronic device of claim 1,comprising a unit for supplying, between the firstelectrically-conductive layer and the second electrically-conductivelayer, a voltage modulated by control signals, the electronic circuit ofeach display pixel circuit being capable of demodulating said voltage toextract the control signals.
 8. The optoelectronic device of claim 7,wherein each electronic circuit comprises a memory having an identifierstored therein, the identifiers stored in the electronic circuits beingdifferent, and wherein each electronic circuit comprises circuitscapable of extracting from the modulated voltage informationrepresentative of one of the identifiers.
 9. The optoelectronic deviceof claim 1, comprising at least one waveguide, coupled to theoptoelectronic circuits of the display pixel circuits and capable ofguiding an electromagnetic radiation.
 10. The optoelectronic device ofclaim 9, wherein the device further comprises a source of saidelectromagnetic radiation coupled with the waveguide and wherein, foreach display pixel circuit, the optoelectronic circuit comprises asensor of said electromagnetic radiation capable of supplying ameasurement signal to the electronic circuit.
 11. The optoelectroniccircuit of claim 10, wherein the source is capable of modulating theelectromagnetic radiation with control signals and wherein, for eachdisplay pixel circuit, the electronic circuit is capable of demodulatingthe measurement signal to extract the control signals.
 12. Theoptoelectronic device of claim 9, comprising at least two waveguides,possibly integrated to the second electrically-conductive layer, coupledto the optoelectronic circuits of different assemblies of said displaypixel circuits.
 13. The optoelectronic device of claim 9, furthercomprising optical coupling means between the waveguide and at leastsome of the display pixel circuits.
 14. A method of manufacturing anoptoelectronic device comprising the steps of: a) manufacturing displaypixel circuits comprising first and second opposite surfaces and eachcomprising an electronic circuit comprising the first surface and athird surface opposite to the first surface, and at least oneoptoelectronic circuit bonded to the third surface and comprising atleast one light-emitting diode, at least one of the electrodes of thelight-emitting diode being connected to the electronic circuit by thethird surface; b) manufacturing a support covered with at least onefirst electrically-conductive layer; c) bonding the first surface of theelectronic circuit of each of at least two display pixel circuits amongthe display pixel circuits to the at least one firstelectrically-conductive layer; d) forming at least one secondelectrically-conductive layer covering at least two display pixelcircuits among the display pixel circuits and electrically coupled, onthe side of the second surface, to the optoelectronic circuit of each ofsaid at least two display pixel circuits covered by said at least onesecond electrically-conductive layer.
 15. The method of claim 14,comprising, between steps c) and d), the step of forming anelectrically-insulating layer covering the first electrically-conductivelayer between the display pixel circuits.
 16. The method of claim 14,wherein step a) comprises forming, for each of the at least two displaypixel circuits covered by said at least one secondelectrically-conductive layer, an electrically-insulating portioncovering the electronic circuit and the optoelectronic circuit and atleast one electrically-conductive element crossing theelectrically-insulating portion and electrically coupled to the secondelectrically-conductive layer and to the optoelectronic circuit or tothe electronic circuit.
 17. The method of claim 15, wherein step a)comprises forming, for each of said at least two display pixel circuitscovered by said at least one second electrically-conductive layer, anelectrically-insulating portion covering the electronic circuit and theoptoelectronic circuit and at least one electrically-conductive elementcrossing the electrically-insulating portion and electrically coupled tothe second electrically-conductive layer and to the optoelectroniccircuit or to the electronic circuit.